Radio receiver gain control



April 1950 A. WESTERVELD 2,503,787

RADIO RECEIVER GAIN CONTROL Filed July 30, 1947 INVENTOR. ADOLF WESTER vs D wg. AZ/

AG'NT Patented Apr. 11, 1950 RADIO RECEIVER GAIN CONTROL Adolf Westerveld,,Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 30, 1947, Serial No. 764,754

In the Netherlands March 5, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 5, 1963 1 v I The invention relates to a radio-receiver with negative feedback in the low-frequency part thereof, which receiver comprises means of controlling the amplification.

In the construction of simple radio-receivers it is important to effectuate the controlof the amplification with the aid of a number of components which is as small as possible. The present invention afiords means of providing a simple radio-receiver with avery effective volume control.

According to the invention, use is above-mentioned radio-receiver both of a highfrequency volume control brought about-with the aid of a potentiometer and of a low-frequency volume control brought about my means of a variable negative feedback, the control of the negative feedback and the high-frequencyvolume control being effected by means of the same potentiometer.

The potentiometer is preferably connected to the voltage to be fed back and, moreover, it is made in the included, at least partly, in the aerial circuit. In this case the regulating contact of the potentiometer is connected, as the case may be, with the interposition of suitable impedances, bothto. the control grid of a high-frequency amplifying: tube or a frequency-changer and to'the' control grid of a low-frequency amplifying tube.

A simple radio-receiver with a particularly effective control of the amplification may be obtained if the said receiver is constructed as a superheterodyne reflex-receiver wherein both the intermediate-frequency oscillations and the lowfrequency oscillations derived therefrom after amplification and detection are amplified in the same discharge system, in which automatic control of the amplification is utilized.

The invention will be explained more fully with reference to the accompanying drawing, which represents the diagram of a superheterodyne re flex-receiver wherein the control of the amplification is efiected in accordance with the invention.

The aerial is connected, through the intermediary of a coupling'condense'r l'; to a potentiometer which consists of two resistances 2 and 3 and which is connected to the secondary terminals of a loudspeaker transformer 4, from which the voltage to be fed back negatively is taken. The regulating contact of the potentiometer is connected, on the one hand, through the intermediary of an input oscillatory circuit 5 which is tuned to the high-frequency oscillations to be received, to the control grid of a heptode system 6 which serves to change the quency and low-frequency volume-controls results 5 Claims. (01. 250-20) frequency and, on the other hand, through the I intermediary of a resistance 1 and an intermediate-frequency circuit which will be described hereinafter, to the control grid of a triode system .8 which operates in reflex-connection. The systems 8 and 6 form together a triode-heptode.

By displacing the regulating contact of the' potentiometer 3, both the high-frequency voltage A on the control grid of the heptode system 6 and the degree of low-frequency'negative feedback of the triode 8 are regulated. In the highest position of the contact the high-frequency voltage has the highest value and the negative feedback is switched off; in the lowest position the highfrequency voltage has the smallest value whereas the degree of the negative feedback is at its maximum. The two controls consequently support one another; this is important in connection with the automatic volume-control utilized for 1 the triode 8, for this' automatic volume-control,

which is necessary in order to avoid overloading of the triode, has the tendency of decreasing the effect of the control of the high-frequency voltage so that, in order to ensure a sufficiently uniform volume control, an additional control in the low- 1 frequency portion is desirable. The combination of the automatic volume control in the reflextube and of the previously described high-frein a particularly effective control of the amplification.

The heptode 6 acts at the same time as an oscillator and to that end it is connected in threepoint connection to an oscillator circuit 9. In

the anode circuit is also incorporated the first circuit of an intermediate-frequency band-pass filter ID the second circuit of which forms part of the control grid circuit of the triode 8. The intermediate-frequency oscillations produced in the anode circuit of the heptode 6 are consequently taken to the control grid of the triode; the amplified oscillations are taken from an intermediate-frequency circuit l I, which is inductively coupled to' the anode circuit of the triode 8 and, for the purpose of rectification, they are 3 between the anode circuit and the control grid circuit.

The amplified low-frequency oscillations which are set up across a resistance IS in the anode circuit of'the triode' 8 are supplied-through a coupling condenser l1 tothe control grid of the pentode portion of the discharge tube 12. In the anode circuit of the pentode is included the pri-" mary winding of the previously mentioned loud speaker transformer 4. secondary winding of this transformer is earthed:

The tuning of the circuits B and 9 to thesignal to be received is preferably efiected' by-"varying" the self-inductance of this circuit with-the aid of slidable iron cores. What I claim is:

1. A receiver circuit arrangement for there' The mid-point of the tion-stage; means to derive an output potential ception of carrier signals having a modulation fr'e I quency component, comprising a carrierfre= quency stag having an input circuit, a modulation frequency stage coupled to -said carrier frequency stage and having. input and output circuitsga potentiometer having a movable tapping; means to derive a negativefeedbackvoltage proportional-to said modulation component from the output circuit of a said modulation frequency stage and to applysaid voltage to the ends of said potentiometer, means to applysaid signals to one nd of said potentiometer, and means to couple the tapping ofsaid potentiometer to the input circuit'of said carrier frequency stage-and,

to-the input circuit of saidmodulation frequency stage.

2; A superheterodyne receiver: circuit arrangement for the reception of :carrier signals having a modulation frequencycomponent, comprising a carrier frequency: mixing; stage having an input circuit, a modulation frequency amplification stage coupled to said carrier-frequency stage and having input and output circuits,- a potentiometer? having a movable tapping, means toderive a: negativefeedback= voltage proportional to saidmodulation component 1 from the output circuit of said modulation frequencyqstage and to apply said voltage: to the ends of said-potentiometer, means to apply: said signalsvto one end of i said potentiometer, and -means to "couple the tapping, of said I potentiometer to: the: input circuit of, said carrier frequency; stage andto-the input cir--- cuit of said-modulation frequency. stage;

3. A reflex receiver circuit arrangement for the 1 reception ofca-rrier signals having a modulation frequency: component, comprising acarrier fr'e-- quencystage having an input circuit, an amplification stage" coupled to I said carrier frequency; stage, a detector stage coupled to said amplification stage, a modulationfrequency stage coupled to said amplification stage and having, an output circuit, means to apply; a portion of the output of said detector-stage to said-amplification stage, a" potentiometer having a-movabletapping, means to derive a negative feedbackv voltage proportional to said modulation component from the output circuit of said modulation frequency. stage and-- to apply said voltagetoithe ends of-said potenti from'said-"dtectorstage, said potential having a first component proportional to said modulation component and a' second component constituting an automatic volume control voltage, means to applyfsaid potential to said amplification stage, a modulation" frequency stage coupled to said amplifi'cation stage and having an output circuit, a potentiometer having a movable tapping, means to-derive a; negative-feedbackvoltageproportional to said modulationcomponent from the output circuit of: saidumodulation frequency stage and: to apply said negative feedbaclc-rvoltage-to theends of said potentiometer, means to apply said signals to one end: of said potentiometer, and; means to couple thetapping ofsaidpotentiometer to theinput circuit of saidcarrier frequency stage and to said amplification stage.

frequency comp0nent,:,c0mprising-; acarrier frequency; stage having- ,an input circuit, a modulation frequencyi stagecoupled to. said carrier fre- I 'quencyysta'ge and having: input andsoutput circults, fi-rst and second resistive elements; one of said resistive elements having a movable tapping,

means to connect together" one end of each of said resistive elements to define a l-junction, means wto derive a negative feedback voltage proportional to said; modulation-component from the output circuit of said modulation" frequency stage and. to apply, said voltage to the other ends of said resistive: elements, means to= apply said signals to 'saidjunction, and means-to couple said tapping, to: the input circuit of said carrier; frequency stage and: to the input I. circuit l of said modula.--

tion frequency stage.

ADOLE WESTERVELD.

REFERENCES CITED The following referencesareof recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 7 1,988,370 Brown Jan. 15, 1935! 1,996,830 Posthumus e1 Apr. -9, 1935 2,115,842 Cooper -May 3, 1938 2,159,453. Senanke 1 May 23, 1939. 2,205,243 Dome June 18, 1940- FOREIGN PATENTS Number Country Date 396,822 GreatBritain Aug.. 1'7, 1933,

5. A receiven circuit arrangementior. the. re-; ception of carrier signals having a modulation 

